Extraction, fractionation and isolation

The air-dried powdered rhizomes of K. foliosa were soaked in 80% methanol at room temperature for 4 days with occasional shaking. Removal of the organic solvent using rotary evaporator (BUCHI Rotavapor™ R-300, Switzerland) followed by freeze drying of the remaining water extract yielded a dark red gummy solid. Portion of the dried extract was dissolved in 5% KOH solution and partitioned with chloroform to remove the nonphenolic components. The aqueous phase was acidified with 2% HCl and then further partitioned with chloroform. The chloroform layer was collected and concentrated in a rotary evaporator to give a dried solid designated crude phenolic fraction I. The reddish solid mass (methanol soluble) formed between the acidified aqueous and chloroform layers was collected as phenolic fraction II. Purification of phenolic fraction I by preparative TLC (Additional file 1: Fig. S1) gave KFP-1 (18 mg, 0.048%). Furthermore, portion of the hydroalcoholic extract was fractionated on silicagel flash column chromatography to yield three fractions. Fraction 1 was eluted with 100% chloroform, fractions 2 and 3 with a mixture of chloroform and methanol (1:1), and fraction 4 with 100% methanol. Fraction 3 was concentrated and freeze dried to give viscous solid, which was further purified by sequential PTLC and solid phase extraction on Isolute C₁₈ columns to give YKFM-2 (14 mg, 0.04%) (Additional file 1: Fig. S2).